Preparation of a test device designed to perform a quantitative test on a given volume of a fluid to provide a visual indication when a certain substance is present in the fluid in an amount in excess of a predetermined amount.
In its preferred embodiment, the test device of the invention is specifically directed to a flat absorbent test patch device used in the screening of persons for cystic fibrosis. Consequently, the invention although of general applicability is described herein with specific reference to its use in screen testing for cystic fibrosis.
A simple screening test is particularly needed for cystic fibrosis because of its high incidence in children. About 1 in 1000 to 1 in 1400 infants are born with cystic fibrosis. Those having cystic fibrosis exhibit high mortality. As recently as 1963 one-third of the deaths from cystic fibrosis occurred in the first year of life; two-thirds in the first five years. The prognosis has recently improved due to early therapy and mortality has decreased to less than five percent in the first year of life. A group half-life of over 20 years can be reasonably expected if treatment is early.
An abnormality which is used to identify persons having cystic fibrosis is the unusually high chloride concentration in their sweat. A sweat chloride concentration significantly greater than normal is constantly present in all persons suffering from this disease.